Honeycomb structures having transverse cross-sectional cellular densities of approximately one tenth to one hundred cells or more per square centimeter have many uses, including as solid particulate filter bodies and stationary heat exchangers. Such uses require selected cells of the structure to be sealed or plugged by manifolding and the like at one or both of the respective ends thereof. The term “sealed” and other corresponding grammatical forms, i.e., sealant, sealing, etc., are used herein to refer to both porous and non-porous methods of closing off the open transverse cross-sectional areas of cells.
For the mass production of such filters and heat exchangers, it is highly desirable to be able to seal selected cell channels ends as rapidly and as inexpensively as possible. Sealing these selected cells comprises inserting a plugging material into the open ends of selected cell channels and subsequently drying the plugged filter. Previous methods for drying have included electromagnetic (EM) drying (e.g., using microwaves), and conventional hot-air drying. The latter includes drying a high porosity ware, such as a green ware, within a drying oven, plugging the open ends of selected cell channels, and re-drying the plugged ware. The process can also be carried out on a fired ware.
This hot-air drying process often results in cracks and stress fractures within the walls of the channels, and filter bodies with a decreased structural integrity. Moreover, these previous techniques are relatively expensive as well as time intensive. Further, existing microwave dryers are generally designed to apply uniform microwave power to the ceramic structure. While this heats the wet plugged ends, it also heats the already-dry or fired regions of the ware. This is inefficient and also tends to overheat the ware, which can lead to structural damage.